This invention relates to a decorative base paper with a modified titanium dioxide and to decorative coating materials produced using this decorative paper base.
Decorative coating materials, the so-called decorative paper or decorative films, are preferably used for surface coating applications in the manufacture of furniture and for interior work. Decorative films should be understood to refer to a synthetic resin-impregnated or synthetic resin-impregnated and surface-treated, printed or unprinted sheet of paper. Decorative films are bonded or glued to a backing sheet.
Depending on the type of impregnation process used, a distinction is made between decorative films with a paper core impregnated throughout and decorative films on pre-impregnated decorative base paper in the case of which the paper is impregnated only partly on line in the paper making machine. High pressure laminates are laminates which are produced by laminating together several impregnated layers of paper placed on top of each other. These high pressure laminates are generally constructed of a transparent overlay providing maximum surface resistance, a synthetic resin-impregnated decorative sheet of paper and one or several phenol resin-impregnated sheets of kraft paper. Hardboard and chipboard panels, for example, as well as plywood are used as the base.
In the case of low pressure laminates, the synthetic resin-impregnated decorative paper is laminated directly to a base such as a chipboard panel by applying low pressure.
The decorative paper used with the above-mentioned coating materials is used in the white or colored state with or without additional overprint.
The so-called decorative base papers used as starting materials for the manufacture of the above-mentioned coating materials need to satisfy particular requirements such as high opacity for a better coverage effect on the base, a homogeneous formation and grammage of the sheet for an even resin absorption, a high light fastness, a high degree of purity and homogeneity of color for a high-quality reproducibility of the pattern to be printed thereon, a high wet strength for a smooth impregnation process, a corresponding absorbency to achieve the required degree of resin saturation and a dry strength satisfactory during reel-up processes in the paper making machine and during printing in the printing machine.
In general, decorative paper base consists of sulphate pulps of extremely bright whiteness, predominantly of hardwood pulp with a high proportion of pigments and fillers and wet strength enhancing agents, retention aids and fixing agents. Decorative base paper differ from the usual types of paper by their very much higher filler component and the fact that they have not undergone core sizing or surface sizing—commonly applied to paper—with well-known sizes such as alkyl ketene dimers.
The opacity is one of the most important properties of decorative base papers. It characterises the covering ability vis-a-vis the substrate.
A high opacity of the decorative paper base is achieved by adding white pigments. Usually titanium dioxide is used as the white pigment. This pigment ensures a high opacity and an excellent brightness and whiteness of the decorative paper base.
When titanium dioxide is fully or partially replaced by other white pigments, this results in a deterioration of these properties. An adjustment of the opacity is possible only by increasing the proportion of the pigment. However, the proportion of pigment used cannot be increased at will since, in this case, a deterioration of the physical properties, such as the retention behaviour of the pulp suspension, the strength, light fastness and resin absorption is to be expected.